In the mail client select the SAP MAPI folder or one of your subfolders.
You identify the folder by the name <SID><CLNT> SAPoffice - <UNAME>, therefore for example C11003 SAPoffice - SMITH for the user Smith in system C11, client 003.
Create a new message. In client MS Outlook, for example, choose File ®
New ® Mail Message.
The corresponding form for creating a message is displayed in MS Outlook.
You can select the message recipient(s) from the SAP address book as it involves a recipient that already exists in the R/3 System.
Choose to... in the MS Outlook form and in the next screen of your SAP address book. If you are in online mode, you can also search for recipients via Find in the R/3 System.
For changeable mails see
Sending Mails 
